DESCRIPTION: The purpose of this proposal is to study the role of kallikrein- binding protein (KBP) in hypertension. Previous studies suggest that the tissue kallikrein-kinin system may be involved in blood pressure regulation. To date, no physiological regulators of this serine proteinase have been identified. With the support of this current grant, the applicants were the first to purify, characterize and clone KBP (designated as kallistatin), a novel serine proteinase inhibitor and putative regulator of the tissue kallikrein-kinin system. They have expressed KBP in heterologous cell expression systems and in transgenic mice. Through genetic analysis, they have found linkage between the KBP gene locus and salt-induced hypertension in spontaneously hypertensive rats. The present goal is to continue to analyze kallistatin's physiological function by the following specific aims. 1)Transgenic mice over-expressing KBP will be developed and these mice will be cross bred to other transgenic mice expressing kallikrein (already available in this laboratory). Phenotypic effects of KBP expression, such as changes in growth, development and blood pressure, will be monitored. The effect of KBP expression on kallikrein-induced hypotension and inflammation will be analyzed in mice carrying both kallikrein and KBP transgene. 2)The kallistatin gene will be inactivated by homologous recombination in mouse embryonic stem cells and its physiological function in these kallistatin-deficient mice will be evaluated. 3)The regulatory elements which control the expression of the KBP gene and the genetic basis of KBP's function in blood pressure regulation linked to the hypertensive phenotype will be analyzed by splicing its 5'- promoter region to a reporter gene and identifying the cis-acting elements and trans-acting factors by deletion analysis, gel retardation and footprinting assays. 4)Potential linkage between the human kallistatin gene and hypertension will be explored by examining affected sibling pairs and family pedigrees. The proposed studies employ multi- disciplinary approaches with state-of-the-art technologies. Understanding the role of kallistatin in the development of hypertension should provide important insights for improving the detection and treatment of cardiovascular diseases and stroke.